個人計算機領域流行用智能電池，這是因為智能電池能提供本個工業標準、高精度氣壓計（gasgauge）系統。智能電池符合智能電池供電系統（SBS）所定義的元件所有工作性能指標，電池具有跟蹤有關電池充電和使用信息的嵌入控制器。通過串行、2線SMBus接口提供信息到系統。可詢問電池信息包括剩余容量、總容量、在現有放電速率下時間余、放電電流、終端電壓等。由于大多數智能電池在總線中可成為主機，所以電池可控制智能電池充電器使其最佳充電。Linear公司LTC1759智能電池充電器IC設計用于控制這類智能電池。另外，由電(dian)(dian)池提供的安全信號指示電(dian)(dian)池是(shi)否呈現在系統中(zhong)和是(shi)否有熱引起的告警或在其(qi)他系統失(shi)效(xiao)時是(shi)否電(dian)(dian)池失(shi)效(xiao)。SBS顯(xian)著特點(dian)是(shi)安全、使(shi)用容易(yi)和兼容性。

　　SBS規范允許兩種類型智能電池充電器（SBC）：Level2充電和Level3充電器。Level2充電器（如LTC1759）是SMBus上的從機，響應來自電池的命令控制充電。Level3充電器可以是SMBus上的主機或從機，它可詢問電池確定充電信息。SBC與電池化學類型無關。它響應來自電池的命令提供充電電流和充電電壓。電池的零電流（或零電壓）或終止充電報警形式發出充電終止。假若安全信號指標電池不存在或安全充電電池太(tai)熱，則充電也將終(zhong)止(zhi)。

　　SMBus 為系(xi)(xi)統(tong)和電(dian)源管理(li)這樣的(de)(de)(de)(de)任務提供了一條控(kong)(kong)制(zhi)(zhi)總線(xian)，使(shi)(shi)用 SMBus 的(de)(de)(de)(de)系(xi)(xi)統(tong)，設備之間發送和接(jie)(jie)收(shou)消息都是(shi)通(tong)過 SMBus，而不是(shi)使(shi)(shi)用單(dan)獨的(de)(de)(de)(de)控(kong)(kong)制(zhi)(zhi)線(xian)，這樣可(ke)以節省設備的(de)(de)(de)(de)管腳(jiao)數。 　　使(shi)(shi)用 SMBus，設備還可(ke)以提供它的(de)(de)(de)(de)生產信(xin)息，告訴系(xi)(xi)統(tong)它的(de)(de)(de)(de)型號(hao)，部(bu)件號(hao)等，針對掛起事件保存(cun)它的(de)(de)(de)(de)狀態，報告不同類別的(de)(de)(de)(de)錯誤，接(jie)(jie)收(shou)控(kong)(kong)制(zhi)(zhi)參(can)數，并返回它的(de)(de)(de)(de)狀態等。 　　SMBus器(qi)件存(cun)在現有7層OSI網(wang)絡模型中(zhong)的(de)(de)(de)(de)前3層，即物理(li)層，數據鏈路(lu)層和網(wang)絡層。 　　SMBus最初的(de)(de)(de)(de)目的(de)(de)(de)(de)是(shi)為智能電(dian)池，充電(dian)電(dian)池和與其他系(xi)(xi)統(tong)通(tong)信(xin)的(de)(de)(de)(de)微(wei)控(kong)(kong)制(zhi)(zhi)器(qi)之間的(de)(de)(de)(de)通(tong)信(xin)鏈路(lu)而定義的(de)(de)(de)(de)。SMBus也(ye)被(bei)用來連接(jie)(jie)各種設備，包括電(dian)源相關設備，系(xi)(xi)統(tong)傳感器(qi)，EEPROM通(tong)訊設備等等。

　　LTC1759是一款完整的Level2智能電池充電器。它能在SMBus接口上用接收和譯碼命令自動充電智能電池。LT1759遵從智能電池充電器規范(fan)的全(quan)(quan)部安全(quan)(quan)要求，包(bao)括(kuo)3分鐘定時器（保(bao)護SMBus通信換效(xiao)和喚(huan)醒模式期間鋰離子電(dian)池過充電(dian)）。硬(ying)件可編程(cheng)電(dian)注和電(dian)壓限制提(ti)供另外(wai)等級(ji)保(bao)護，這種(zhong)保(bao)護由(you)失效(xiao)軟件不可能改變。

　　LTC1759管理智能電池充電系統的所有復雜事物。它具有SBC依從性、安全、輸出電壓精確、SMBus加速泵、墻式適配器電流限制等特性。它把智能充電器的恒流（CC）、恒壓（CV）、電流模式開關電池充電器電路融合于一身。

　　電路描述

　　LTC1759包括：一個同步、電流模式、PWM降壓開關控制器，一個充電器控(kong)制(zhi)(zhi)器(qi)，兩個控(kong)制(zhi)(zhi)充電(dian)器(qi)參量的10位DAC，一個熱(re)敏電(dian)阻(zu)安全(quan)信號譯(yi)碼器(qi)，硬件電(dian)壓和電(dian)流限制(zhi)(zhi)譯(yi)碼器(qi)和一個SMBus控(kong)制(zhi)(zhi)器(qi)單元（見圖1）。

 智能電(dian)(dian)池或系(xi)統控制器通過(guo)SMBus接口命令對恒漢和恒壓(ya)限值進行編程。降(jiang)壓(ya)變壓(ya)器用N-溝MOSFET做(zuo)為開(kai)關，使成本降(jiang)低、高效率(lv)工作。熱敏電(dian)(dian)阻安(an)全檢(jian)測電(dian)(dian)路檢(jian)測電(dian)(dian)池存在(zai)或確定電(dian)(dian)池溫度是否允(yun)許安(an)全充(chong)電(dian)(dian)。

當通(tong)過(guo)SMBus傳輸接收(shou)恒流(liu)(liu)(liu)(liu)值(zhi)時，它被RILIMIT定標和限制到低于編(bian)程(cheng)值(zhi)。此修正值(zhi)編(bian)程(cheng)電(dian)(dian)流(liu)(liu)(liu)(liu)DAC，設置DC充(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)(liu)(liu)。電(dian)(dian)流(liu)(liu)(liu)(liu)DAC是10位△∑DAC，當希望(wang)充(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)(liu)(liu)時，它從(cong)PROG引腳吸(xi)收(shou)電(dian)(dian)流(liu)(liu)(liu)(liu)（見圖2）。放大器PROG引腳吸(xi)收(shou)電(dian)(dian)流(liu)(liu)(liu)(liu)（見圖2）。放大器CAI感(gan)測RSENSE上(shang)的壓(ya)降并使(shi)此電(dian)(dian)壓(ya)跨接到RS2（200Ω）；流(liu)(liu)(liu)(liu)經RS2的電(dian)(dian)流(liu)(liu)(liu)(liu)通(tong)過(guo)電(dian)(dian)流(liu)(liu)(liu)(liu)鏡像(xiang)做(zuo)為PROG引腳上(shang)的上(shang)接電(dian)(dian)流(liu)(liu)(liu)(liu)。流(liu)(liu)(liu)(liu)經RS2電(dian)(dian)流(liu)(liu)(liu)(liu)與(yu)來自(zi)PROG引腳電(dian)(dian)流(liu)(liu)(liu)(liu)相匹配(pei)由CA2實現恒流(liu)(liu)(liu)(liu)工作。由于DAC輸出(chu)是一串脈(mo)沖，所以需(xu)要平滑電(dian)(dian)容器對脈(mo)沖濾波(bo)使(shi)其變為DC。

  LTC1759需(xu)要兩(liang)個電(dian)(dian)源。PWM電(dian)(dian)路(lu)在墻(qiang)式適配器電(dian)(dian)源斷(duan)開時(shi)(shi)(shi)(shi)直接通過(guo)Vcc引(yin)腳(jiao)運(yun)行(xing)(xing)，邏(luo)輯(ji)(ji)功(gong)能(neng)(neng)運(yun)行(xing)(xing)與(yu)VDD電(dian)(dian)源無關。PWM電(dian)(dian)路(lu)在去掉AC電(dian)(dian)源時(shi)(shi)(shi)(shi)能(neng)(neng)進入40μA微功(gong)率(lv)停(ting)機(ji)模式，使(shi)邏(luo)輯(ji)(ji)和SMBus工作能(neng)(neng)保持運(yun)行(xing)(xing)，這是(shi)Intel ACPI標準所需(xu)要的(de)。這種分離電(dian)(dian)源也使(shi)邏(luo)輯(ji)(ji)和SMBus能(neng)(neng)根(gen)據(ju)系統設計為(wei)員的(de)需(xu)要運(yun)行(xing)(xing)在3V和5V.為(wei)使(shi)LTC1759邏(luo)輯(ji)(ji)功(gong)耗最小，邏(luo)輯(ji)(ji)電(dian)(dian)流(liu)由(you)時(shi)(shi)(shi)(shi)鐘電(dian)(dian)路(lu)激勵，時(shi)(shi)(shi)(shi)鐘電(dian)(dian)路(lu)當無動作時(shi)(shi)(shi)(shi)停(ting)機(ji)并蘇醒服務(wu)于(yu)SMBus動作或產生中斷(duan)。一旦請求服務(wu)，LTC1759便返(fan)回到休眠。

　　當去掉(diao)AC電(dian)源(yuan)或(huo)去掉(diao)電(dian)池時，通(tong)過CHGEN-SDB引(yin)腳(jiao)組合發生PWM停(ting)機(ji)。LTC1759通(tong)過DCDIV通(tong)腳(jiao)檢測AC損耗。閾(yu)值通(tong)常設置恰好低于墻(qiang)式適配(pei)的最小有(you)效電(dian)壓。AC電(dian)源(yuan)狀態通(tong)過SMBus可由系統讀出(chu)。UV引(yin)腳(jiao)只用于置PWM電(dian)路(lu)進入微功(gong)率停(ting)機(ji)狀態，它(ta)直(zhi)接(jie)連(lian)到(dao)墻(qiang)式適配(pei)器電(dian)源(yuan)。

　　在設(she)計(ji)中電感器選擇(ze)不是(shi)(shi)關鍵，這是(shi)(shi)因為(wei)充電器的環路(lu)響應在意地設(she)置很(hen)慢。實際的低限值為(wei)15μH左(zuo)右(you)，低值電感器將產生較(jiao)高(gao)的紋波電流，在輸出需要較(jiao)低ESR電容器。

　　輸(shu)(shu)出電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)的(de)選擇(ze)(ze)對(dui)ESR（等效(xiao)串(chuan)聯電(dian)(dian)(dian)(dian)阻(zu)）不是很(hen)苛刻(ke)，但必須處理來自(zi)充(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)的(de)所有(you)紋波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)流。不用(yong)考慮電(dian)(dian)(dian)(dian)池(chi)的(de)紋波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)流，因為(wei)(wei)充(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)有(you)效(xiao)阻(zu)抗(kang)遠遠大(da)于(yu)電(dian)(dian)(dian)(dian)感器(qi)(qi)的(de)ESR。很(hen)多電(dian)(dian)(dian)(dian)池(chi)組具有(you)內部串(chuan)聯保護(hu)MOSFET，這提高了電(dian)(dian)(dian)(dian)池(chi)ESR。在(zai)(zai)多電(dian)(dian)(dian)(dian)池(chi)配置(zhi)中也(ye)有(you)與(yu)電(dian)(dian)(dian)(dian)池(chi)串(chuan)聯的(de)功率(lv)路(lu)由(you)MOSFET，進(jin)一(yi)步增(zeng)加了電(dian)(dian)(dian)(dian)池(chi)ESR。從(cong)充(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)觀點(dian)，輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)ESR可高達1Ω，使電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)選擇(ze)(ze)范(fan)圍(wei)寬。當采用(yong)電(dian)(dian)(dian)(dian)阻(zu)或電(dian)(dian)(dian)(dian)子負(fu)載時，可能會發生某種不穩定性。增(zeng)加300Ω電(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)與(yu)PROG引腳電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)串(chuan)聯或在(zai)(zai)輸(shu)(shu)出置(zhi)10μF電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)能改善穩定性。在(zai)(zai)輸(shu)(shu)出不需要(yao)用(yong)陶瓷(ci)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)，因為(wei)(wei)在(zai)(zai)很(hen)輕負(fu)載電(dian)(dian)(dian)(dian)流聲頻下開(kai)關(guan)變(bian)換器(qi)(qi)變(bian)得(de)不連(lian)接(jie)和在(zai)(zai)下降(jiang)周期開(kai)始時電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)會造成噪聲，應該采用(yong)鉭(tan)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)。輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)選擇(ze)(ze)由(you)充(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)輸(shu)(shu)入(ru)紋波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)流（一(yi)般為(wei)(wei)最大(da)輸(shu)(shu)出電(dian)(dian)(dian)(dian)流的(de)1/2）決(jue)定。對(dui)于(yu)4A充(chong)電(dian)(dian)(dian)(dian)器(qi)(qi)建議用(yong)22μF（50V）陶瓷(ci)電(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)(rong)器(qi)(qi)，它一(yi)般可處理2A紋波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)流。

　　從電(dian)(dian)(dian)(dian)池(chi)(chi)到(dao)墻式(shi)適配(pei)(pei)器(qi)的(de)(de)電(dian)(dian)(dian)(dian)流保(bao)護由P-溝MOSFET（Q1）提供(gong)。電(dian)(dian)(dian)(dian)壓(ya)(ya)比較器(qi)監控(kong)跨接(jie)在MOSFET上的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)而且當墻式(shi)適配(pei)(pei)降到(dao)電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)之上小于(yu)200mV時關閉(bi)MOSFET。盡(jin)管(guan)價廉(lian)的(de)(de)二極管(guan)可用于(yu)替代以MOSFET，但MOSFET只增加(jia)100mV到(dao)0.4V低壓(ya)(ya)差(cha)工作模式(shi)而不產(chan)生額(e)外的(de)(de)熱(re)量。在沒有電(dian)(dian)(dian)(dian)池(chi)(chi)起動時間，采用MOSFET附加(jia)二極管(guan)使(shi)墻式(shi)適配(pei)(pei)器(qi)電(dian)(dian)(dian)(dian)源能達到(dao)Vcc引腳并(bing)為PWM控(kong)制電(dian)(dian)(dian)(dian)路(lu)供(gong)電(dian)(dian)(dian)(dian)。

　　主要(yao)的補償是d PROG引(yin)腳(jiao)上進(jin)行；然而DAC脈(mo)沖濾(lv)波要(yao)求確定電(dian)(dian)(dian)容(rong)器(qi)有效值。脈(mo)沖紋波電(dian)(dian)(dian)流必須小平200mV或環路(lu)(lu)起伏（在輕載充電(dian)(dian)(dian)電(dian)(dian)(dian)流時(shi)出現的環路(lu)(lu)不穩定性(xing)）。Vc引(yin)腳(jiao)電(dian)(dian)(dian)容(rong)器(qi)的主要(yao)功能(neng)是提供自(zi)啟動支持。必須有一個1.5K電(dian)(dian)(dian)阻器(qi)與Vc引(yin)腳(jiao)電(dian)(dian)(dian)容(rong)器(qi)串聯以能(neng)恰當(dang)停機。

　　從熱觀點考慮，輸(shu)出(chu)電(dian)壓(ya)在電(dian)池溫度(du)充電(dian)范圍內(nei)保持大(da)約0.5%精度(du)。精度(du)越高，電(dian)流充電(dian)容量(liang)就(jiu)越大(da)，而更(geng)重要(yao)是在電(dian)池中與電(dian)壓(ya)基充電(dian)終端電(dian)路有(you)關的問題(ti)就(jiu)會更(geng)少。

　　關于SMBus加速泵，AC適配電(dian)流限制，安(an)全信號感測(ce)，安(an)全電(dian)壓和(he)電(dian)流范圍設計等問(wen)題在(zai)此就不(bu)一(yi)一(yi)詳述。

　　LTC1579遵從智能電池系統組織發表的智能電池充電器標準。充電器控制器也遵從Intel的ACP標準，甚至當沒有AC墻式適配器電源時也能響應系統指令。該充電器提供最寬的電流和電壓工作范圍。LTC1759具有價廉、高性能和安全的特點，比其他智能電池充電器優越。